Time scales in dense granular flows
Abstract: Dense granular flows demonstrate complicated behavior the in fluid-solid transition. Some of these behaviors are caused by different time scales in the particle interactions.
Kinetic theory applies if the mean free flight time of a particle is large compared to the binary interactions. For a dense granular system, this condition is not satisfied. Formation of particle cluster significantly prolongs the particle interactions. Investigation of probability distribution of particle interaction time leads to a spectrum of particle interaction time scales. Depending the dominating particle interaction time scale, granular flows can behavior like non-linear viscous fluid, linear viscous fluid, history-dependent viscoelastic fluid or solid. Similarity and difference between dense granular flows and polymeric materials are discussed.